Brake



' April 17, 1934.

T. DAVIDSON 1,954,801

BRAKn Filed Aug. 26, 1929 Favor Davidson,

I N V EN TOR.

31 1 19 Wei/ A TTORNEYS.

Patented Apr. 17, 1934 UNITED STA BRAKE Trevor Davidson, Milwaukee, Wis., assignor to Bucyrus-Erie Company,

South Milwaukee, Wis,,

a corporation of Delaware Application August 26, 1929, Serial No. 388,599

7 Claims. (cuss-1'1 My invention relates to new and useful improvements in band brakes, and has for its principal object to provide a means for taking up and releasing the slack in brake bands.

Heretofore, the chief practical operating difficulty with large diameter band brakes on heavy excavating machinery, particularly when actuated by a foot lever, has been that so large a part of the travel of the lever has had to be devoted merely to taking up and releasing the slack in the brake band, that either a very short lever with consequent loss of leverage is required, or too much travel of the lever for convenient foot-operation.

A further difficulty has been that the limited play of the brake lever has never permitted a sufficient slacking off of the brake band to enable adequate cooling of the band between its successive applications and this fact has resulted in,

- great and undue wear on both band and drum.

These difficulties have been solved by U. S. Patent No. 1,646,718, to Wilkinson and Lehman, for improvements in Brakes, patented October 25, 1927, by affixing to the dead end of the brake band a take up mechanism, which is actuated by (the, first slight movement of the control lever;

but this has the disadvantage that this mechanism must be able to hold the dead end of the brake band against the tremendous tension to which that end is subjected during braking.

Accordingly it is my more particular object to devise a means whereby, not only the brake setting, but also the slack taking up can both be applied to the live end of the band.

My invention admits all the advantages set forth in the above mentioned patent, and in addition, due to this last mentioned feature, enables me to employ a slack take -up mechanism which is neither as strong nor as powerful as in the former constructiomand is hence less expensive and less likely to get out of order. Other advantages of my design will naturally suggest themselves as the description progresses. It is within the province of the disclosure to improve generally and to enhance the utility of devices of that type to which the invention appertains.

With these general objects in view, the inven tion resides in the novel features of construction, combination and arrangement of parts which will be hereinafter more particularly described and claimed, and shown in the accompanying drawing.

Figure 1 is a side view of the apparatus, partly in section.

Figure 2 is an edge view of the floating lever and associated parts, taken along the line 2-2 in Figure 1.

Referring more particularly to the drawing, it will be seen that 1 represents a cross-section of the shaft to be braked. Keyed to this shaft 69 is a brake-drum 2, in braking contact with which are the blocks 3 of a brake-band 4. The shaft and drum rotate counterclockwise, as indicated by the curved arrow.

The dead-end 5 of the brake-band is fixed at 6, in the conventional manner, the live-end 7 of the brake-band is pivoted at 8 to the short arm 9 of a bell crank, which in turn is pivoted at 10. To the long arm 11 of this bell crank is attached a rod 12.

13 is a floating lever, supported in any convenient manner. As shown, it is supported at 14 by support 15 which is pivoted at 16 to a bracket 15a, depending from the main frame 1'7 of the machine.

The rod 12 is attached to the lever 13 at 18, which thus constitutes the end of the short arm of this lever, the fulcrum being at 19.

At 20 on this lever is attached a rod 21, the otherend of which is attached at 22 to link 23." Link 23 is pivoted at 24 to the main frame 'of the machine. i

The upper end of link 23 is pivoted at 25 to the elbow of link 26. Foot lever 27'is pivoted at 28 to the main frame-of the machine, and is attached at 29 to thelin'k 26.

The operating lever 30 of an admission and release valve 31 bears against the face 32 of the foot lever 2'7, said face being so curved that the first slight downward motion of the foot lever will move i the handle of the valve to its full open position, and that subsequent downward motion of the foot lever will not alter the setting of the valve.

A pipe 33 admits steam to this valve from a source not shown. Pipe 34 leads away the en'- haust from this valve. When this valve is opened, it admits steam through pipe 35 to cylinder 36, thereby forcing piston 37 and piston rod 38 to the right. Piston rod 38, being attached to floating lever 13 at its fulcrum 19, shifts this fulcrum against adjustable stop 39, thereby shifting the position of the fulcrum and taking up the slack I in the brake band 4. The stop should be so adjusted that this shifting of the fulcrum will merely take up the slack, without having any appreciable braking effect,

Further downward motion of the foot lever 27, operates through the linkage formed by links 26 and 23, and the rod 21 on the long arm 20 of the lever 13, and thence to the short arm. 18 of this lever, and rod 12, and bell crank 9-11, to apply braking pressure to the live-end 7 of the brake-band 4, in any desired-degree. 1

Upon releasing the foot pressure on the foot lever 27, the weight 40 restores the foot lever to its initial position. The final upward movement of the foot lever releases handle 30 of valve 31, this lever being then restored to its original position by spring 41. This motion' of the handle closes the valve to the source and opens it to exhaust the cylinder 36. The release of'steam pressure in the cylinder 36 permits spring 42 to move the fulcrum 19 of the floating lever 13 to the left, thus restoring all the slack in the brake-band 4.

The valve 31 is not shown in detail, such valve being well known to those skilled in the art.

It is evident that any convenient form of control lever can be substituted for foot lever 27. In

fact, my invention does not inhere at all in this lever and its associated mechanism. Accordingly I do not intend to be limited to any particular control means, nor for that matter to any particular type of power for shifting the fulcrum of floating lever 13.

I claim:

1. In a brake, the combination of: a rotating shaft; a brake drum thereon; a brake-band for frictional engagement with the drum; means for setting and releasing the brake by motion of the live end of the brake-band; and distinct means, operating in advance of the first mentioned means to take up, and in arrears of the first mentioned means to restore, the slack in the brake-band by motion of the'live end thereof, said last named means consisting in a fluid operated piston.

2. In a brake, the combination of a rotating shaft; a brake drum thereon; a brake-band for frictional engagement with the drum; means. for setting and releasing the brake by motion of the live end of the brake-band; and distinct means, operating in advance of the first mentioned means to take up, and in arrears of the first mentioned means to restore, the slack in the brake-band by motion of the live end thereof, said first named means consisting in a brake-lever, said last named means consisting in a fluid operated piston.

3.v In a brake, the combination of: a rotating shaft; a brake drum thereon; a brake-band for frictional engagement with the drum; means for setting and releasing the brake by motion of the live end of the brake-band; and independent means for takingup and restoring the slack in the brake-band by motion of the live end thereof, said first named means consisting in a brakelever, said last named means consisting in a fluid operated piston, controlled by a part of the motion of said brake-lever.

4. In a brake, the combination of: .a rotating 1 setting and releasing the brake by'motion of the live end of the brake-band; and independent means for taking up and restoring the slack in the brake-band by motion of the live end thereof; said first named means consisting in a brakelever, said last named means consisting in a fluid operated piston, controlled by a part of the motion of said brake-lever acting through an admission and release valve.

5. In a brake, the combination of: a rotating shaft; a brake drum thereon; a brake-band for frictional engagement with the drum; means for setting and releasing the brake by motion of the live end of the brake-band; independent means for taking up the slack in the brake-band by motion of the live .end thereof, said first named means consisting in a brake-lever, said last named means consisting in a fluid operated piston, controlled by a part of the motion of said brake-lever acting through an admission and releasevalve; and spring means for restoring the slack in the brake-band.

6. In a brake, the combination of: a rotating shaft; a brake drum thereon; a brake-band for frictional engagement wtih the drum; a lever, having a fulcrum and two arms; means operatively connecting one arm to the live end of the brake-band; an adjustable stop; fluid-pressure means for shifting the fulcrum to abut the stop; separate means for moving the other arm of the lever; and a common control mechanism, controlling said means for shifting the fulcrum, and said means for moving the other arm of the lever.

'7. In a mechanism for shifting the position of a machine element, the combination of: a floating lever, having a fulcrum and two arms; means operatively connecting one arm with the machine element to be shifted; fluid pressure means for moving at will the position of the fulcrum; an adjustable stop for positively limiting the motion of the fulcrum; separate means for moving the other arm of the lever; and a control lever; the parts being so contrived and arranged that the first slight motion of the control lever moves the fulcrum ofthe floating lever to take up slack in the element operated on, and that subsequent motion of the control leverrmovest the aboveated on.

TREVOR DAVIDSON. 

